USDA researchers are trying to determine how much high soil acidity and aluminum toxicity are affecting Washington crops.

They recently conducted an anonymous survey of farmers hoping to learn more about acid soil. They are asking if farmers have noticed declining pH levels in their soil, the range of pH levels and what they have done to mitigate the impacts.

Researchers at first estimated 30,000-50,000 acres in and around Spokane and Latah counties had acid soils, but Tim Paulitz, USDA Agricultural Research Service root disease researcher, expects to find more affected areas.

Soil acidity is found in areas that were formerly wooded or where bluegrass production took place.

Where pH levels have dropped, indicating more acidity, aluminum damages plants' roots, resulting in low yields. In some areas, farmers have had to switch to winter triticale or timothy hay because they can no longer economically grow wheat.

Washington State University spring wheat breeder Mike Pumphrey says the varieties Babe and particularly Whit are fairly tolerant of acidic soils. Seed increases are taking place for a planned winter release of a new hard red spring wheat that's particularly tolerant of acid soils, Pumphrey said.

Pumphrey advises growers that in marginal soil, Whit will exhibit minimal effects of aluminum toxicity. But in "highly toxic" areas aluminum tolerance in the wheat is not enough. Those sites can see yield reductions of 50 or 60 percent, he said.

Pumphrey recommends farmers continue to test their soil. He also encouraged them to consider the cost-effectiveness of lime.

"Even if it's expensive, there's some growers out there that could really benefit from that expensive treatment," he said. "If they can figure out a way to finance it, that investment's probably going to pay off in a one- to two-year time frame on some of the worst sites."

One of the challenges is that there is no source of lime in the region, Pumphrey said.

Pumphrey said that "pHs continue to decline. Even soils that aren't there yet are going to be there as we look forward a decade or two. Don't be afraid to start doing something about it, because it's only getting worse."

Eastern Washington farmers have virtually no experience with liming, but it's common practice in Oregon's Willamette Valley, Paulitz said.

For more information, contact WSU Spokane County Extension Specialist Diana Roberts at robertsd@wsu.edu or 509-477-2167.